Browsing by Author "Gemi, Dilek Soylu"

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Citation - WoS: 59
Citation - Scopus: 59
Experimental Investigation of Axial Compression Behavior After Low Velocity Impact of Glass Fiber Reinforced Filament Wound Pipes With Different Diameter
(Elsevier Sci Ltd, 2022) Gemi, Dilek Soylu; Şahin, Ömer Sinan; Gemi, Lokman
The GRP (Glass Reinforced Polymer) composite pipes produced by filament winding (FW) technique are used in many applications such as the transmission of pressurized gases, liquids, oil, and natural gas transmission. These composite pipes may be subjected to low velocity impacts during production and/or service for various reasons. The impact on the composite pipes may lead to invisible damages such as matrix crack, fiber damage, and inter layer separation. In this study, pipes with three different diameters (empty set54, empty set72, and empty set96 mm) were produced to investigate the damage caused by low velocity impact and to determine the effect of these damages on the strength losses of the composite pipe. The pipes were subjected to low velocity impact test according to ASTM D 7136 with 1.5, 2, 2.5, and 3 m/s impact velocities. In order to examine the effects of impact damages on the strength of pipes, Compression after impact (CAI) tests were performed on pre-damaged pipes according to ASTM D 7137 and Force-Displacement and Stress-Strain relations were obtained. The results of impacted samples were compared with the behavior of undamaged samples. After the experiments, macro/micro damage analyses of GRP pipes were performed by optical microscope and SEM imaging.
Citation - WoS: 73
Citation - Scopus: 79
Experimental Investigation of the Effect of Diameter Upon Low Velocity Impact Response of Glass Fiber Reinforced Composite Pipes
(ELSEVIER SCI LTD, 2021) Gemi, Dilek Soylu; Şahin, Ömer Sinan; Gemi, Lokman
The GRP (Glass Reinforced Polymer) composite pipes produced by filament winding technique are used in many fields such as the transmission of pressurized chemical liquids, industrial liquids, oil and natural gas transmission and construction materials. GRP composite pipes may be subjected to low velocity impacts for various reasons both during installation and service. The impact on the GRP composite pipe wall may lead to some nonvisible damages such as matrix crack, fiber damage, delamination and inter-layer separation. Composite pipes suffered strength loss due to these damages caused by impact cannot support the expected strength values during service. Pipes with three different diameters (054, 072 and 096 mm) were produced to investigate the damage caused by low velocity impact and to determine the effect of these damages on the strength losses of the composite pipe. In order to investigate the influence of low velocity impact damage, the produced pipes were subjected to impacts at the velocity of 1.5, 2, 2.5 and 3 m/s according to ASTM D 7136 and preliminary damage was formed. During low velocity impact tests, Force-Time, Force-Displacement and Energy-Time graphs were obtained and dynamic behavior of the pipes were examined. With the increase in diameter; it has been observed that the effect of low velocity impact is reduced and the damage after impact transformed into delamination damage rather than multiple damage.
Citation - WoS: 121
Citation - Scopus: 130
An Experimental Study on the Effects of Various Drill Types on Drilling Performance of Gfrp Composite Pipes and Damage Formation
(ELSEVIER SCI LTD, 2019) Gemi, Lokman; Morkavuk, Sezer; Köklü, Uğur; Gemi, Dilek Soylu
Drilling is the most commonly used machining operation among others for assembly applications. The necessity of this operation has come to the forefront in composite materials that are becoming widespread nowadays. In this study, drilling performance of glass fiber reinforced plastic (GFRP) composite pipes used in many sectors such as natural gas transmission lines, pressurized sewer lines, industrial waste transmission, defense industry, and construction industry was investigated. The GFRP pipe was produced by filament winding method with a winding angle of +/-55 degrees. Different drill types (conventional twist drill, brad and spur drill, and brad center drill) with a drill diameter of 4 mm were utilized for drilling the pipe and the effect of drill type on the drilling performance was investigated. Drilling tests were performed at a constant 5000 rpm spindle speed and six different feed rate parameters (25, 75, 125, 175, 225, and 275 mm/min). Thrust forces generated during drilling were recorded and after the drilling operations, hole exit surface damage, and borehole surface damage were examined by a digital microscope and scanning electron microscope (SEM). Results showed that the brad center drill produced lower thrust forces while the twist drill generated higher thrust forces. The severity of damages could vary depending on the tool geometry and feed rate. Especially, at lower feed rates, conventional twist drill results with increased delamination and uncut fibers as compared with other drills. The brad center drill presents better performance since it generates fewer damages. Also, it is observed that these damages formed in the winding angle direction (orientation).
Filaman Sarım Ctp Borularda Darbe Sonrası Basma (caı) Davranışının İncelenmesi
(Konya Teknik Üniversitesi, 2019) Gemi, Dilek Soylu; Şahin, Ömer Sinan
Filaman sarım tekniği ile üretilen CTP (Cam Takviyeli Polimer) kompozit borular basınçlı kimyasal madde içeren sıvıların, endüstriyel sıvıların iletiminde, petrol ve doğalgaz iletimi ve çeşitli alanlarda konstriksiyon malzemesi olarak birçok alanda kullanılmaktadır. CTP kompozit borular gerek montaj gerekse servis esnasında çeşitli sebeplerden dolayı düşük hızlı darbelere maruz kalabilmektedir. Darbenin etkisiyle CTP kompozit boru cidarında; matris çatlağı, elyaf hasarı ve tabakalar arası ayrılma gibi gözle görülmeyen hasarlar meydana gelebilir. Darbe sonucu oluşan bu hasarlar ile mukavemet kaybına uğrayan kompozit borular, servis esnasında beklenen mukavemet değerlerini verememektedir. Düşük hızlı darbe sonrası oluşan hasarların incelenmesi ve bu hasarların kompozit borunun mukavemet kayıplarına etkisinin araştırılması için (±55°)3 konfigürasyonuna sahip üç farklı çapta (Ø54, Ø72 ve Ø96 mm) kompozit boru üretilmiştir. Düşük hızlı darbe hasarının etkisinin incelenmesi amacıyla, yukarıda belirtilen çaplardaki borular üzerine ASTM D 7136 standardına göre, 1.5, 2, 2.5 ve 3 m/s hızlarda darbe uygulanmış ve ön hasar oluşturulmuştur. Düşük hızlı darbe sırasında Kuvvet-Zaman, Kuvvet-Deplasman ve Enerji-Zaman grafikleri çıkartılarak boruların dinamik davranışları ve oluşan hasarlar incelenmiştir. Darbe sonrası borularda oluşan hasarların kalan mukavemete etkilerinin incelenebilmesi için ön hasarlı borulara ASTM D 7137 standardına göre Darbe Sonrası Basma (CAI) testleri yapılmış ve Kuvvet-Deplasman grafikleri elde edilmiştir. Elde edilen sonuçlar, darbe hasarsız numunelerin davranışlarıyla karşılaştırılmıştır. Düşük hızlı darbe ve darbe sonrası basma deneyleri sırasında elde edilen veriler ve oluşan hasarlar kaydedilmiştir. Deneyler sonrasında CTP boruların optik mikroskop ve SEM görüntüleme ile makro/mikro hasar analizleri yapılmıştır